Abstract

Eight promising genotypes were studied for three seasons (1989-1991) at Agricultural Research Station, Amberpet to evaluate their stability for grain and straw yields under kharif conditions. There was a significant variation for genotypes and genotype x environment interaction for grain as well as for straw yields. Both linear and non-linear components were significant and between the two the linear component was higher in magnitude. Harsha appeared to be the most promising dual purpose variety, where as Varun and Ashwini were found to be suitable for grain and straw yields respectively.

Maize (Zea Mays L) is next in important to rice as a valuable food-cum-fodder crop in Andhra Pradesh. It is grown under different edaphic and environmental conditions and it is known to exhibit a high degree of genotype environment interaction. There is an especial need to recommend varieties suitable for both grain and fodder purposes during kharif season with stability in performance over a wide range of environmental conditions. The present study therefore, was under taken to evaluate promising varieties of grain-cum-fodder maize in multienvironmental tests in order o identify a high yielding and stable genotype before their final recommendation to the farmer

Materials and Methods

The experimental material consisting of 8 promising composites of maize (including a variety ‘ROHINI’ as check) was sown in a randomized block design with three replications at Maize Research Station, Amberpet, Hyderabad during the kharif seasons of 1989 to 1991 (3 years) in black soil. The plot size was 5.0 x 3.0 m2 and each plot accommodated four rows spaced at 75 cm between rows and 20 cm between plants with in a row, respectively.

Usual and recommended package of practices were attended so as to raise an healthy crop. Observations on total plant basis/plot was recorded for grain yield and also for straw yield. Stability parameters were worked out using the mean plot yield (Grain as well as straw yield )obtained over year and the statistical model as suggested by Eberhart and Russel (1966)

Results and Discussion

Mean grain and straw yield of the eight genotypes (Table1) in general was low during 1989. As evidenced from the native environmental index value for the year, the season could be considered as a poor environment. Pooled analysis of variance (Table 2 ) showed that mean squares for environment were highly significant against genotype-environment mean squares, where as varieties were found to be significant for grain as well as for straw yield with lower magnitude varieties, environment (Linear) , variety x environment (linear) and non-linear component of genotype-environment interaction were highly significant. It further revealed that the genotypes reacted considerable with the environmental conditions that existed in diffemt years of testing. In the similar studies Rao (1986) observed that a large portion of the genotype x environment interaction in maize was accounted by the linear component and the non-linear component was comparatively small but significant.

Mean grain as wel as straw yield and the two stability parameters viz. regression co-efficient (bi) and deviation from regression (S2di) for 8 genotypes are given in Table-3. The linear regression analysis of facilities in identification genotypes with wider adaptability over a range of environments. A genotype with high mean, unit regression co-efficient (bi=1.00) and least deviation from regression (S2di=0) is considered as an ideal widely adopted and stable genotype (Eberhart and Russel, 1966). Further it has, however , been emphasized by Jatasara and Paroda (1980) that liner regression could be considered as a measure of stability, the genotype with least deviation around the regression being the most stable and vice versa. According to these criteria, Harsha and Varun with high mean grain yields were the most stable and composite B101, through it gave on par yield to that of Varun, was the least stable genotype-where as for straw yield, Ashwini and Harsha appeared to be the most desirable check

“Rohini” and composite B 104 along with other varieties were unstable for both the characters. Therefore, from the results it can be concluded that, varun and Ashwini could be considered desirable for grain and straw yields, respectively, where as Harsha appeared to be themost promising dual purpose genotype.

Table: 1. Mean yield of genotypes in different seasons.

Genotype

Grain yield (q/ha)

Straw yield (q/ha)

1989

1990

1991

Mean

1989

1990

1991

Mean

Harsha

Comp.B-101

Varun

Comp.B-102

Ashwini

Comp. B 103

Comp.B 104

Rohini (Check)

Mean

Environment index

32.1

29.6

26.7

23.4

22.1

20.9

28.3

21.0

25.5

-4.3

34.4

39.4

34.0

33.3

34.6

33.3

24.1

22.1

31.9

2.1

34.3

29.4

37.2

29.8

31.8

32.8

33.3

28.3

32.1

2.2

33.6

32.8

32.6

28.6

29.5

29.0

28.6

23.9

29.8

29.5

23.8

27.8

23.8

27.4

26.4

28.5

26.5

26.7

-4.8

34.2

33.3

32.3

28.8

36.0

35.4

31.2

39.6

33.8

2.3

35.8

30.4

32.7

30.3

36.9

34.3

35.2

36.4

34.0

2.5

33.2

29.2

30.9

27.6

33.4

32.0

31.6

34.2

31.5

Table: 2. Analysis of variance of grain and straw yield.

Source of variation

d.f

Mean squares

Grain yield (q/ha)

Straw yield(q/ha)

Genotypes(G)

Environment(E)

G x E

E + G x E

E(Linear)

G x E (Linear)

Pooled Deviation

(Non-liner)

Pooled error

7

2

14

16

1

7

8

42

29.59..

84.73..

12.68..

27.06.

224.50..

11.27..

15.19

1.67

14.84..

37.58..

7.89..

19.81.

277.72..

3.63..

2.86

0.32

.. Significant at 0.01 levels

Table: 3. Mean yields and parameters of stability of different maize genotypes